src/osx/core/glgrab.cpp

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  31  */
  32
  33 #if wxOSX_USE_COCOA_OR_CARBON
  34
  35 #import <CoreFoundation/CoreFoundation.h>
  36 #import <ApplicationServices/ApplicationServices.h>
  37 #import <OpenGL/OpenGL.h>
  38 #import <OpenGL/gl.h>
  39
  40 #include "wx/osx/private/glgrab.h"
  41
  42 extern CGColorSpaceRef wxMacGetGenericRGBColorSpace();
  43
  44 /*
  45  * perform an in-place swap from Quadrant 1 to Quadrant III format
  46  * (upside-down PostScript/GL to right side up QD/CG raster format)
  47  * We do this in-place, which requires more copying, but will touch
  48  * only half the pages.  (Display grabs are BIG!)
  49  *
  50  * Pixel reformatting may optionally be done here if needed.
  51  */
  52 static void swizzleBitmap(void * data, int rowBytes, int height)
  53 {
  54     int top, bottom;
  55     void * buffer;
  56     void * topP;
  57     void * bottomP;
  58     void * base;
  59
  60
  61     top = 0;
  62     bottom = height - 1;
  63     base = data;
  64     buffer = malloc(rowBytes);
  65
  66
  67     while ( top < bottom )
  68     {
  69         topP = (void *)((top * rowBytes) + (intptr_t)base);
  70         bottomP = (void *)((bottom * rowBytes) + (intptr_t)base);
  71
  72
  73         /*
  74          * Save and swap scanlines.
  75          *
  76          * This code does a simple in-place exchange with a temp buffer.
  77          * If you need to reformat the pixels, replace the first two bcopy()
  78          * calls with your own custom pixel reformatter.
  79          */
  80         bcopy( topP, buffer, rowBytes );
  81         bcopy( bottomP, topP, rowBytes );
  82         bcopy( buffer, bottomP, rowBytes );
  83
  84         ++top;
  85         --bottom;
  86     }
  87     free( buffer );
  88 }
  89
  90
  91 /*
  92  * Given a display ID and a rectangle on that display, generate a CGImageRef
  93  * containing the display contents.
  94  *
  95  * srcRect is display-origin relative.
  96  *
  97  * This function uses a full screen OpenGL read-only context.
  98  * By using OpenGL, we can read the screen using a DMA transfer
  99  * when it's in millions of colors mode, and we can correctly read
 100  * a microtiled full screen OpenGL context, such as a game or full
 101  * screen video display.
 102  *
 103  * Returns a CGImageRef. When you are done with the CGImageRef, release it
 104  * using CFRelease().
 105  * Returns NULL on an error.
 106  */
 107
 108 CGImageRef grabViaOpenGL(CGDirectDisplayID display, CGRect srcRect)
 109 {
 110     CGContextRef bitmap;
 111     CGImageRef image;
 112     void * data;
 113     long bytewidth;
 114     GLint width, height;
 115     long bytes;
 116
 117     CGLContextObj    glContextObj;
 118     CGLPixelFormatObj pixelFormatObj ;
 119     GLint numPixelFormats ;
 120     CGLPixelFormatAttribute attribs[] =
 121     {
 122         kCGLPFAFullScreen,
 123         kCGLPFADisplayMask,
 124         (CGLPixelFormatAttribute) 0,    /* Display mask bit goes here */
 125         (CGLPixelFormatAttribute) 0
 126     } ;
 127
 128
 129     if ( display == kCGNullDirectDisplay )
 130         display = CGMainDisplayID();
 131     attribs[2] = (CGLPixelFormatAttribute) CGDisplayIDToOpenGLDisplayMask(display);
 132
 133
 134     /* Build a full-screen GL context */
 135     CGLChoosePixelFormat( attribs, &pixelFormatObj, &numPixelFormats );
 136     if ( pixelFormatObj == NULL )    // No full screen context support
 137         return NULL;
 138     CGLCreateContext( pixelFormatObj, NULL, &glContextObj ) ;
 139     CGLDestroyPixelFormat( pixelFormatObj ) ;
 140     if ( glContextObj == NULL )
 141         return NULL;
 142
 143
 144     CGLSetCurrentContext( glContextObj ) ;
 145     CGLSetFullScreen( glContextObj ) ;
 146
 147
 148     glReadBuffer(GL_FRONT);
 149
 150
 151     width = (GLint)srcRect.size.width;
 152     height = (GLint)srcRect.size.height;
 153
 154
 155     bytewidth = width * 4; // Assume 4 bytes/pixel for now
 156     bytewidth = (bytewidth + 3) & ~3; // Align to 4 bytes
 157     bytes = bytewidth * height; // width * height
 158
 159     /* Build bitmap context */
 160     data = malloc(height * bytewidth);
 161     if ( data == NULL )
 162     {
 163         CGLSetCurrentContext( NULL );
 164         CGLClearDrawable( glContextObj ); // disassociate from full screen
 165         CGLDestroyContext( glContextObj ); // and destroy the context
 166         return NULL;
 167     }
 168     bitmap = CGBitmapContextCreate(data, width, height, 8, bytewidth,
 169                                    wxMacGetGenericRGBColorSpace(), kCGImageAlphaNoneSkipFirst /* XRGB */);
 170
 171
 172     /* Read framebuffer into our bitmap */
 173     glFinish(); /* Finish all OpenGL commands */
 174     glPixelStorei(GL_PACK_ALIGNMENT, 4); /* Force 4-byte alignment */
 175     glPixelStorei(GL_PACK_ROW_LENGTH, 0);
 176     glPixelStorei(GL_PACK_SKIP_ROWS, 0);
 177     glPixelStorei(GL_PACK_SKIP_PIXELS, 0);
 178
 179     /*
 180      * Fetch the data in XRGB format, matching the bitmap context.
 181      */
 182     glReadPixels((GLint)srcRect.origin.x, (GLint)srcRect.origin.y, width, height,
 183                  GL_BGRA,
 184 #ifdef __BIG_ENDIAN__
 185                  GL_UNSIGNED_INT_8_8_8_8_REV, // for PPC
 186 #else
 187                  GL_UNSIGNED_INT_8_8_8_8, // for Intel! http://lists.apple.com/archives/quartz-dev/2006/May/msg00100.html
 188 #endif
 189                  data);
 190     /*
 191      * glReadPixels generates a quadrant I raster, with origin in the lower left
 192      * This isn't a problem for signal processing routines such as compressors,
 193      * as they can simply use a negative 'advance' to move between scanlines.
 194      * CGImageRef and CGBitmapContext assume a quadrant III raster, though, so we need to
 195      * invert it. Pixel reformatting can also be done here.
 196      */
 197     swizzleBitmap(data, bytewidth, height);
 198
 199
 200     /* Make an image out of our bitmap; does a cheap vm_copy of the bitmap */
 201     image = CGBitmapContextCreateImage(bitmap);
 202
 203     /* Get rid of bitmap */
 204     CFRelease(bitmap);
 205     free(data);
 206
 207
 208     /* Get rid of GL context */
 209     CGLSetCurrentContext( NULL );
 210     CGLClearDrawable( glContextObj ); // disassociate from full screen
 211     CGLDestroyContext( glContextObj ); // and destroy the context
 212
 213     /* Returned image has a reference count of 1 */
 214     return image;
 215 }
 216
 217 #endif